Tandon 810 won't boot or format

[dukes909]

8 hours ago, TZJB said:

I have been through your readings:-

Ok I redid this with logic probe set to TTL and drive on but at rest. Readings much different:

 

8 hours ago, TZJB said:

Pin 24 is the 1 MHz clock so doesn't look right. Maybe check it with the 'scope and also determine whether you are using A202 or Z101A to generate it.

Pin 24 scope pic:

A204, same pin (24):

Z101, pin 11:

8 hours ago, TZJB said:

For Pin 38 to be low while reading indicates there is no assembled data? Or is it inverted? Better check this one again with the 'scope.

 

Pin 38 (2 snaps):

 

[dukes909]

3 minutes ago, kheller2 said:

Got a 1050 or 850 laying around?

I have both! The 1050 is the only working drive I have right now so would rather not possibly mess it up, lol. I have an 850 I never hooked up so I don't know if that would be a good swap but I would rather try that first.   Now to find it....lol

[TZJB]

11 hours ago, dukes909 said:

Ok I redid this with logic probe set to TTL and drive on but at rest. Readings much different:

 

Pin 24 scope pic:

A204, same pin (24):

Z101, pin 11:

Pin 38 (2 snaps):

 

 

I can say with certainty that the 1 MHz clock is working great!

 

With pin 3 high, the chip is not selected. Not sure anything else will be valid now so maybe this was a rabbit hole, but it showed states are changing and that there is data on the bus.

 

We can ignore pins 15-17 as they are not used.

 

Pin 25 has to be low as it is grounded in this instance in order to select an external Data Separator. In older versions of the Atari 810 it is +5V to use the Internal Data Separator.

 

Pin 26 is a Floppy Disk clock so is pulsing.

 

Pin 30 is the Write Gate and only goes high when writing.

 

Pin 31 is Write Data and only pulses when writing. It makes you wonder what SAMS was doing with their Atari 810 when they produced the logic table.

 

Pin 35 is the Index Pulse and should be held high in idle. This looks wrong. Maybe there is a disk in the drive, maybe half in?

 

Pin 38 at 200mV looks like noise....Not sure but it looks wrong.

 

11 hours ago, dukes909 said:

I have both! The 1050 is the only working drive I have right now so would rather not possibly mess it up, lol. I have an 850 I never hooked up so I don't know if that would be a good swap but I would rather try that first.   Now to find it....lol

 

An Atari 850 has two RIOT chips so maybe substitute the one in the Atari 810 for diagnostic purposes.

 

Can you run the CPS 810 Diagnostic cartridge?

 

Maybe follow the FSM Ver. 3 flow charts from page 8B-22 for write logic troubleshooting which will also encompass reading.

 

 

 

 

 

 

 

 

 

 

 

 

 

[dukes909]

11 hours ago, TZJB said:

An Atari 850 has two RIOT chips so maybe substitute the one in the Atari 810 for diagnostic purposes.

I tried one of the 2 6532's from the 850 in the 810 and same results: won't read anything off the disk and won't format either.

11 hours ago, TZJB said:

Can you run the CPS 810 Diagnostic cartridge?

I don't have a copy of the CPS 810 cartridge. Is there an ATR I can download to try booting off the FujiNet device? For some reason I thought cartridge images weren't possible to boot off of? I'm still learning FujiNet.

Even if I had it, reading the description on Best's page: "(requires an Oscilloscope and 5 1/4 Alignment Disk and Stepper program)"... I have the scope but no idea where to get the alignment disk and stepper program..?

11 hours ago, TZJB said:

Maybe follow the FSM Ver. 3 flow charts from page 8B-22 for write logic troubleshooting which will also encompass reading.

Looks like this requires the CPS 810 cartridge...

[dukes909]

11 hours ago, TZJB said:

Pin 38 at 200mV looks like noise....Not sure but it looks wrong.

 

Ok I tried it again with the other sideboard I have and it looks like the same results. 

 

Drive trying to read:

and a single edge triggered shot:

However, when trying to do a format on this drive, I get something remarkably different on pin 38:

But the format never completes. The head moves towards the spindle hole formatting (at least what I remember formatting sounding like), then when it gets near to the spindle, it just spins and spins and spins and spins.... I have to power off the drive for it to stop, and the disk is not formatted properly.  

Beginning to give up hope on this drive. 😞

 

[TZJB]

9 hours ago, dukes909 said:

I tried one of the 2 6532's from the 850 in the 810 and same results: won't read anything off the disk and won't format either.

I don't have a copy of the CPS 810 cartridge. Is there an ATR I can download to try booting off the FujiNet device? For some reason I thought cartridge images weren't possible to boot off of? I'm still learning FujiNet.

Even if I had it, reading the description on Best's page: "(requires an Oscilloscope and 5 1/4 Alignment Disk and Stepper program)"... I have the scope but no idea where to get the alignment disk and stepper program..?

Looks like this requires the CPS 810 cartridge...

 

You have the original fault of not reading the disk, but we know it's not the RIOT chip!

 

The diagnostics programs are available from Atarimania http://www.atarimania.com/list_utilities_atari_search_100.105.97.103.110.111.115.116.105.99._8_U.html.

 

An alignment disk can be made on your own 1050 disk drive. It won't be official but at least both drives would be able to read it. It would normally be a formatted disk made on a master duplicating machine. Not sure there are any now.

 

Unfortunately the 810 Diagnostic is for Cartridge media so unless you have an AVGCart or other cartridge emulator, you can't run it unless you physically make your own or blow a ROM to fit an existing 8KB Cartridge.

 

810 Diagnostic Cartridge (1982)(Atari)(US).bin

 

I have not tried it but maybe some 1050 diagnostics will work?

 

1050_Disk_Diagnostics_1983_Atari.atr

 

Incidentally one of the 810 FSM Tech Tip 6 mentions changing a resistor value:-

 

 

 

 

 

[TZJB]

10 hours ago, dukes909 said:

Ok I tried it again with the other sideboard I have and it looks like the same results. 

 

Drive trying to read:

and a single edge triggered shot:

However, when trying to do a format on this drive, I get something remarkably different on pin 38:

But the format never completes. The head moves towards the spindle hole formatting (at least what I remember formatting sounding like), then when it gets near to the spindle, it just spins and spins and spins and spins.... I have to power off the drive for it to stop, and the disk is not formatted properly.  

Beginning to give up hope on this drive. 😞

 

 

You are getting close to the problem. Could you please show the waveforms using both of the inputs at the FD1771 pins 26 & 27 while reading? This is the data going in to the FDC which needs to be verified as it may be causing the problem.

 

Also reading the FD1771 datasheet this seems relevant regarding pin 38 DRQ (sorry for the cut and paste):-

 

 

 

So at the moment the DRQ is staying low during the read operation but going high during the write operation. Both operations should be going high.

 

Also even though it doesn't complete can you confirm that the data is erased? i.e format a disk in your 1050 in single density and write DOS to it, re-format in the 810 and wait for failure. Re-read in the 1050 to see if it's erased or good.

[+kheller2]

[dukes909]

9 hours ago, TZJB said:

Incidentally one of the 810 FSM Tech Tip 6 mentions changing a resistor value:-

 

Good catch. Unfortunately mine are already 1.4K's.  Working through the steps in your next post now.

[dukes909]

10 hours ago, TZJB said:

Could you please show the waveforms using both of the inputs at the FD1771 pins 26 & 27 while reading? This is the data going in to the FDC which needs to be verified as it may be causing the problem.

Of course you wanted 2 adjacent pins checked on the bottom side of that chip at the same time! Just kidding. That was quite a challenge but I think I got it. Yellow 26, purple 27..

Autoset on the scope:

and then single trigger mode:

Horizontal scale widened:

\

10 hours ago, TZJB said:

format a disk in your 1050 in single density and write DOS to it, re-format in the 810 and wait for failure. Re-read in the 1050 to see if it's erased or good.

Formatted in 1050 using DOS 2.0.

Wrote DOS files to it in 1050.

Booted to verify - good.

Started "Format" in 810.... now 10 minutes have elapsed, drive is still spinning and no error returned in DOS so far. How long do I wait?

[+kheller2]

9 minutes ago, dukes909 said:

Of course you wanted 2 adjacent pins checked on the bottom side of that chip at the same time! Just kidding. That was quite a challenge but I think I got it. Yellow 26, purple 27..

Autoset on the scope:

and then single trigger mode:

Horizontal scale widened:

\

Formatted in 1050 using DOS 2.0.

Wrote DOS files to it in 1050.

Booted to verify - good.

Started "Format" in 810.... now 10 minutes have elapsed, drive is still spinning and no error returned in DOS so far. How long do I wait?

A format should only be slightly longer than in the 1050, say 30 seconds?   I think you can test the disk in the 1050 now.

[dukes909]

After 20 minutes I hit BREAK on ATARI; the drive eventually stopped (after about 2 minutes). DOS returned an "ERROR 128". I tried the disk in the 1050 and it doesn't read anything, just the grinding sound and then an ERROR 144. 🤔

[dukes909]

2 minutes ago, kheller2 said:

A format should only be slightly longer than in the 1050, say 30 seconds?   I think you can test the disk in the 1050 now.

I know but @TZJB said "wait for failure". I thought eventually it would return an error.

[dukes909]

As an interesting aside, after the intital format attempt where the head moves towards the spindle, and stops, after about 5-6 minutes (I know, I should have timed it), it starts what looks like the end of a format and then stops again. Then it starts this cycle again after about 5-6 minutes.

https://www.youtube.com/shorts/u1S8zTP5s-0

Edited July 8, 2023 by dukes909
typos

[TZJB]

11 hours ago, dukes909 said:

Of course you wanted 2 adjacent pins checked on the bottom side of that chip at the same time! Just kidding. That was quite a challenge but I think I got it. Yellow 26, purple 27..

Autoset on the scope:

and then single trigger mode:

Horizontal scale widened:

\

Formatted in 1050 using DOS 2.0.

Wrote DOS files to it in 1050.

Booted to verify - good.

Started "Format" in 810.... now 10 minutes have elapsed, drive is still spinning and no error returned in DOS so far. How long do I wait?

 

Thanks for the readings, the signal looks rough so you have found the fault!

 

Sorry you had trouble getting them, I previously suggested you pick those signals up from A205 due to inaccessibility.

 

There are a few components on the Data Separator board supporting the Data inputs of the FD1771.

 

A208 - 74LS04

A205 - 74LS08

A201, A207 - 74LS74.

A204, A206 - 74LS193.

 

If we go back to J103 pin 27, the signal looks clean into the Data Separator board which then goes to A201 pin 11, the 74LS7474 flip-flop.

 

 

Please check the output at A201 pin 6 or 13.

 

Then at A 204 pin 12 and A206 pin 7.

 

Followed by A205 pin 8 and A205 pin 11.

 

I expect that you are following my drift here as you are looking to find where the signal degrades.

 

Because of the feedback to A206 you may have to resort to substitution of the components.

 

 

 

[TZJB]

12 hours ago, dukes909 said:

After 20 minutes I hit BREAK on ATARI; the drive eventually stopped (after about 2 minutes). DOS returned an "ERROR 128". I tried the disk in the 1050 and it doesn't read anything, just the grinding sound and then an ERROR 144. 🤔

 

Sorry I did assume there would be an automatic error generated from what you said, but you got there. ERROR 128 means BREAK!

 

Regarding the format, it proves that the erase head is behaving correctly and because the drive can't read I think it can't write the directory sectors. So it is behaving as expected at this point.

[TZJB]

12 hours ago, dukes909 said:

As an interesting aside, after the intital format attempt where the head moves towards the spindle, and stops, after about 5-6 minutes (I know, I should have timed it), it starts what looks like the end of a format and then stops again. Then it starts this cycle again after about 5-6 minutes.

https://www.youtube.com/shorts/u1S8zTP5s-0

 

It looks like it is seeking to write the directory but can't find the sector so you need to fix it! 😁

[dukes909]

It looks maybe like multiple failures???....

14 hours ago, TZJB said:

Please check the output at A201 pin 6 or 13.

Pin 6:

15 hours ago, TZJB said:

A 204 pin 12

15 hours ago, TZJB said:

A206 pin 7

15 hours ago, TZJB said:

A205 pin 8

15 hours ago, TZJB said:

A205 pin 11

[TZJB]

7 hours ago, dukes909 said:

It looks maybe like multiple failures???....

 

 

Hopefully it's just the A201 74LS74 flip-flop that has gone faulty. Try replacing this with the A207 from your other card and see if the signal improves.

 

 

Edit: Please confirm the waveform at A201 pin 11 though, which should be the same as J103 pin 27.

Edited July 10, 2023 by TZJB

[dukes909]

15 hours ago, TZJB said:

Edit: Please confirm the waveform at A201 pin 11 though, which should be the same as J103 pin 27.

J103 pin 27 autoset:

and single trigger mode:

15 hours ago, TZJB said:

Hopefully it's just the A201 74LS74 flip-flop that has gone faulty. Try replacing this with the A207 from your other card and see if the signal improves.

Reads still fail (🤨), but A201 pin 6 looks better than the one above (I think...not really sure what it is supposed to look like 🤔)??...

Single trigger mode:

 

[TZJB]

13 hours ago, dukes909 said:

J103 pin 27 autoset:

and single trigger mode:

Reads still fail (🤨), but A201 pin 6 looks better than the one above (I think...not really sure what it is supposed to look like 🤔)??...

Single trigger mode:

 

 

That looks a lot squarer, but I think that you may need to adjust your probe to show a squarer signal. Shame changing the 74LS74 didn't fix it yet, though. Obviously leave that one in now.

 

Looking back, your observation regarding multiple failures may be correct.

 

There may be a problem with A206 as the output is a bit wonky (technical term) so definitely substitute that one from your other board also. Then if the fault persists record some more waveforms at A206 pin 7 and A205 pin 8. If they are not similar, change A205 too. Lastly change A207 if it's still not playing ball.

 

 

[Chri O.]

I just quickly looked through this thread not sure if the track sensor 0 was tested yet ?

The reason is in one of the videos I can hear the drive stepper motor making noise but the head is not moving.

[dukes909]

On 7/11/2023 at 10:47 AM, TZJB said:

That looks a lot squarer, but I think that you may need to adjust your probe to show a squarer signal.

Do you mean adjust the low-frequency compensation adjustment screw on the probe? I ask because when I check the test waveform built into the scope I get a perfectly square signal:

Working on the rest of your suggestions...was away for a couple of days so it's going to take a bit to get caught up. Thanks

[+kheller2]

On 7/11/2023 at 1:03 PM, Chri O. said:

I just quickly looked through this thread not sure if the track sensor 0 was tested yet ?

The reason is in one of the videos I can hear the drive stepper motor making noise but the head is not moving.

810s do not have that, they have a stop screw.  Wacka wacka.  

[Chri O.]

Ohh OK -- Wacka wacka 😁